Field of the Invention
The invention relates to a device for preventing re-use of a container for supplying ink to an ink printing head.
Such ink printing heads are used both in typical office printers and in small high-speed printers. The latter are components of modern machines for printing addresses or for product labeling and will soon also be part of machines for applying postage to mail.
The function of the printing heads should be assured in such a way that if at all possible no missing ink dots will occur. That is important not only for the sake of the printed image quality in general but also and in particular for security-relevant printed image data, such as the monetary value, the date and the serial number of the machine in the case of postage printing. If missing ink dots and damage to the printing head are to be prevented, among other requirements the supply of the proper ink for the ink printing head must be absolutely assured to be as free of bubbles as possible.
It is usual (see German Patent DE 27 09 730 C2) for the ink connecting line from the ink printing head to the container for the ink supply, which is referred to below as the fresh ink container, to be docked on the ink container through a hollow needle. The ink container is provided with a rubber-elastic closure that is pierced by the hollow needle. That prevents both the invasion of air into the ink connecting line and an unintended escape of ink from the ink container. With that docking principle, however, it is possible that partly or entirely emptied fresh ink containers may be refilled with any arbitrary ink by unauthorized persons and inserted into the printer. That can cause failure or even damage to the ink printing head.